OBS Lua Control Visca-over-IP based cameras 2.6

This updated improves the Visca implementation:

• Fix for a resource leak; socket connections were not closed, claiming a new connection for every send command.
• Connections are now re-used for each camera. This also means that the message counter (part of the Visca protocol header) is now used properly.

This updated includes a few enhancements and minor changes to the documentation:

• The visibility (enabled/disable) of the Visca plugin source is now respected. When the plugin is disabled in a scene, the action is not executed.
• A new options is added to the source settings of the plugin to run an action on preview only when the camera is not active on program. This prevents accidental changes to the camera as long as it is live for broadcasting.